GB2059314A

GB2059314A - Using a water curtain to cool a continuous casting

Info

Publication number: GB2059314A
Application number: GB7933677A
Authority: GB
Original assignee: Davy Loewy Ltd
Current assignee: Davy Loewy Ltd
Priority date: 1979-09-28
Filing date: 1979-09-28
Publication date: 1981-04-23

Abstract

Continuous casting apparatus is provided with means for producing a coherent curtain of cooling liquid on at least one surface of the casting, the curtain extending transverse to the direction of movement of the casting. If desired, curtains of cooling liquid may be applied to opposite surfaces of the casting or to each surface of the casting, this being particularly so when the casting is a bloom, billet or slab. The water curtain may be of the type described in UK Patent Specification 2006647A.

Description

SPECIFICATION Water curtain for use with continuous casting apparatus This invention relates to the continuous casting of metal in the form of blooms, billets or slabs and is particularly concerned with the so-called secondary cooling of the metal as it emerges from the casting mould.

It has been recognised that there is a need for intensive secondary cooling of the casting to stabilise its outer skin to thereby reduce the danger of the casting bulging in the space between adjacent pairs of pinch rollers which conventionally act on the casting. Such bulging is known to be a cause of undesirable internal cracking, and those steels which are particularly susceptible to internal cracking require special attention to be paid to uniform cooling.

Unsatisfactory secondary cooling is known to be responsible for the formation of surface cracks.

In an attempt to reduce bulging, the distance between the adjacent pairs of pinch rollers which act on the casting has been reduced as much as possible.

As a consequence, the size of the nozzles which are used to emit the secondary cooling jets of water between the rollers has also had to be reduced, and this has led to frequent failure of the jets due to clogging of the nozzles by impurities.

In the case where a cast slab passes directly into a rolling mill stand from the caster, a high degree of uniformity of cooling across the slab is essential.

Without this uniformity of cooling, the defect known as "striping" occurs and leads to non-uniformity of reduction during the rolling operation.

It is sometimes required to vary the degree of cooling on opposite sides of the casting in order to assist in bending the casting after it has left the mould and/orto assist in straightening the casting after it has achieved its desired directional change of path. This operation requires a readily and accurately controllable water cooling system and it has been found that conventional nozzles are not sufficiently controllable to achieve this end.

We have now found that the use of a water curtain fulfils the requirements of all the above conditions. A water curtain of the type described in British patent applications Nos.4932/77 and 2,006,647A is found to give the intensity of cooling necessary to eliminate the danger of bulging between pairs of adjacent pinch rollers. Further, a uniform degree of cooling of the casting across its width is achieved with such a curtain, which is not possible when using conventional jets. Thus no "striping" occurs and better results are obtained when rolling follows immediately after the casting operation.

We have found that the elongated nozzle for producing a water curtain is more readily and accurately adjustable than are the nozzles of conventional jets and therefore the desired degree of cooling imparted to the casting is more readily obtained. This is found to be beneficial when definitive cooling is utilised to cause the strip to bend after emerging from the mould, or alternatively after its change of direction has been accomplished.

It has also been observed that an elongated water curtain nozzle is less liable to failure due to clogging by impurities in the water than conventional nozzles, this being advantageous in the requirements of uniform cooling across the slab.

In the case of casting blooms or billets, water curtains are employed on all sides of the emerging casting, and again the intensity of cooling and the degree of control of the flow of coolant have been found far superior to that of conventional spray nozzles.

The water curtain as above described is found to be equally successful whether the casting emerges from the mould vertically or horizontally.

Preferably the water curtain impinges on the adjacent surfaces of the workpiece transverse to the path of movement of the workpiece.

1. Continuous casting apparatus comprising a continuous casting mould, means for introducing molten metal into the mould, means for withdrawing a casting from the mould and means downstream of the mould for cooling the casting, characterised in that the cooling means comprises apparatus for providing a coolant curtain of cooling liquid to at least one surface of the casting, the curtain extending in a direction transverse to the direction of movement of the casting.

2. Continuous casting apparatus as claimed in claim 1, in which apparatus for providing a coherent curtain on each of a pair of opposite surfaces of the casting is provided.

3. Continuous casting apparatus as claimed in claim 1, in which apparatus for providing a coherent curtain on each surface of the casting is provided.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Water curtain for use with continuous casting apparatus This invention relates to the continuous casting of metal in the form of blooms, billets or slabs and is particularly concerned with the so-called secondary cooling of the metal as it emerges from the casting mould. It has been recognised that there is a need for intensive secondary cooling of the casting to stabilise its outer skin to thereby reduce the danger of the casting bulging in the space between adjacent pairs of pinch rollers which conventionally act on the casting. Such bulging is known to be a cause of undesirable internal cracking, and those steels which are particularly susceptible to internal cracking require special attention to be paid to uniform cooling. Unsatisfactory secondary cooling is known to be responsible for the formation of surface cracks. In an attempt to reduce bulging, the distance between the adjacent pairs of pinch rollers which act on the casting has been reduced as much as possible. As a consequence, the size of the nozzles which are used to emit the secondary cooling jets of water between the rollers has also had to be reduced, and this has led to frequent failure of the jets due to clogging of the nozzles by impurities. In the case where a cast slab passes directly into a rolling mill stand from the caster, a high degree of uniformity of cooling across the slab is essential. Without this uniformity of cooling, the defect known as "striping" occurs and leads to non-uniformity of reduction during the rolling operation. It is sometimes required to vary the degree of cooling on opposite sides of the casting in order to assist in bending the casting after it has left the mould and/orto assist in straightening the casting after it has achieved its desired directional change of path. This operation requires a readily and accurately controllable water cooling system and it has been found that conventional nozzles are not sufficiently controllable to achieve this end. We have now found that the use of a water curtain fulfils the requirements of all the above conditions. A water curtain of the type described in British patent applications Nos.4932/77 and 2,006,647A is found to give the intensity of cooling necessary to eliminate the danger of bulging between pairs of adjacent pinch rollers. Further, a uniform degree of cooling of the casting across its width is achieved with such a curtain, which is not possible when using conventional jets. Thus no "striping" occurs and better results are obtained when rolling follows immediately after the casting operation. We have found that the elongated nozzle for producing a water curtain is more readily and accurately adjustable than are the nozzles of conventional jets and therefore the desired degree of cooling imparted to the casting is more readily obtained. This is found to be beneficial when definitive cooling is utilised to cause the strip to bend after emerging from the mould, or alternatively after its change of direction has been accomplished. It has also been observed that an elongated water curtain nozzle is less liable to failure due to clogging by impurities in the water than conventional nozzles, this being advantageous in the requirements of uniform cooling across the slab. In the case of casting blooms or billets, water curtains are employed on all sides of the emerging casting, and again the intensity of cooling and the degree of control of the flow of coolant have been found far superior to that of conventional spray nozzles. The water curtain as above described is found to be equally successful whether the casting emerges from the mould vertically or horizontally. Preferably the water curtain impinges on the adjacent surfaces of the workpiece transverse to the path of movement of the workpiece. CLAIMS